ios - 将值传递给闭包函数

Question

检查这段代码:

func getReversedGeocodeLocation(location: CLLocation, completionHandler: @escaping ()->()) {
    CLGeocoder().reverseGeocodeLocation(location, completionHandler: {(placemarks, error) -> Void in

        if error != nil {
            print("Reverse geocoder failed with error" + error!.localizedDescription)
            return
        }

        if placemarks != nil {
            if placemarks!.count > 0 {
                let pm = placemarks![0]
                if let addressDictionary: [AnyHashable: Any] = pm.addressDictionary,
                let addressDictionaryFormatted = addressDictionary["FormattedAddressLines"] {
                    let address = (addressDictionaryFormatted as AnyObject).componentsJoined(by: ", ")
                    self.addressInViewController = address
                }
                completionHandler()
            }
        } else {
            print("Problem with the data received from geocoder")
        }
    })
}

在 View Controller 中

override func viewDidLoad() {
    var addressInViewController = String()
    getReversedGeocodeLocation(location: location, completionHandler: {
        print("After geo finished")
    })
}

这是一个使用闭包的简单案例。如您所见，当反向地理完成时，它会更新在函数本身之外定义的 addressInViewController 变量。关于闭包，我有点困惑，但我知道它本质上是将另一个函数作为参数传递给一个函数。那么我是否可以传入类似 (_ String: x)->() 而不是 ()->() 的内容，其中地址变量将从主要的反向地理函数中填充并传递？我试过这样做，但它说“x”是未定义的。如果这是可行的，那么我想我可以使用闭包以更好的方式解耦我的代码。

谢谢，祝你有美好的一天:)

Answer 1

像这样定义你的方法

func getReversedGeocodeLocation(location: CLLocation, completionHandler: @escaping (_ value : Any)->()) {
    CLGeocoder().reverseGeocodeLocation(location, completionHandler: {(placemarks, error) -> Void in

        if error != nil {
            print("Reverse geocoder failed with error" + error!.localizedDescription)
            return
        }

        if placemarks != nil {
            if placemarks!.count > 0 {
                let pm = placemarks![0]
                if let addressDictionary: [AnyHashable: Any] = pm.addressDictionary,
                let addressDictionaryFormatted = addressDictionary["FormattedAddressLines"] {
                    let address = (addressDictionaryFormatted as AnyObject).componentsJoined(by: ", ")
                    self.addressInViewController = address
                }
                completionHandler(address)
            }
        } else {
            print("Problem with the data received from geocoder")
        }
    })
}

override func viewDidLoad() {
    var addressInViewController = String()
    getReversedGeocodeLocation(location: location, completionHandler: { (_ values : Any) in
         self. addressInViewController = values

    })
}

根据您的需要制作 Value 的数据类型。